234 MOUNTING AND PRESERVATION OF OBJECTS. 



remounted, so soon as the fluid has escaped to such a degree as to 

 leave any considerable portion of it uncovered. 



173. Importance of Cleanliness. — The success of the result of 

 any of the foregoing operations is greatly detracted-from, if, in 

 consequence of the adhesion of foreign substances to the glasses 

 whereon the objects are mounted, or to the implements used in 

 the manipulations, any extraneous particles are brought into view 

 with the object itself. Some such will occasionally present them- 

 selves, even under careful management ; especially fibres of silk, 

 wool, cotton, or linen, from the handkerchiefs, &c, with which the 

 glass-slides may have been wiped ; and grains of starch, which 

 often remain obstinately adherent to the thin-glass covers kept 

 in it. But a careless and uncleanly manipulator will allow his 

 objects to contract many other impurities than these ; and espe- 

 cially to be contaminated by particles of dust floating through the 

 air, the access of which may be readily prevented by proper pre- 

 cautions. It is desirable to have at hand a well-closed cupboard 

 furnished with shelves, or a cabinet of well-fitted drawers, or a 

 number of bell-glasses upon a flat table, for the purpose of securing 

 glasses, objects, &c, from this contamination in the intervals of 

 the work of preparation ; and the more readily accessible these 

 receptacles are, the more use will the Microscopist be likely to 

 make of them. Great care ought, of course, to be taken that the 

 Liquids employed for mounting should be freed by effectual filtra- 

 tion from all floating particles ; and both these and the Canada 

 Balsam should be kept in well-closed bottles. 



174. Labelling and Preserving of Objects. — Whenever the 

 mounting of an object has been completed, its name ought to be 

 at once marked on it, and the slide should be put away in its 

 appropriate place. Some inscribe the name on the glass itself 

 with a writing diamond ; whilst others prefer to gum a label* on 

 the slide ; and others, again, cover one or both surfaces of the 

 slide with coloured paper, and attach the label to it. In the case 

 of objects mounted dry or in balsam, the latter method has the 

 advantage of rendering the glass-cover more secure from dis- 

 placement by a slight blow or 'jar,' when the varnish or balsam 

 may have become brittle by the lapse of years. Instead, how- 

 ever, of attaching the white label on which the name of the object 

 is written, to the outside of the coloured paper with which the slide 

 is covered, it is better to attach the label to the glass, and to punch 

 a hole out of the coloured paper, sufficiently large enough to show 

 the name, in the part corresponding to it: in this manner the 

 label is prevented from falling off, which it frequently does when 

 attached to the glass without protection, or to the outside of the 

 paper cover. When objects are mounted in fluid, either with or 



* Very neat gummed labels, of various sizes and patterns suitable to 

 the wants of the Microscopist, are sold by the ' Drapers' Stationers ' in 

 the City. 



